The present invention relates generally to digital signal processing, and more particularly to generation and application of sample rate conversion ratios using distributed jitter.
Digital signal processing (DSP) is widely used to perform a variety of functions, such as filtering, compression, enhancement, and others. Generally, an analog signal is preprocessed and sampled at a particular sampling frequency using an analog-to-digital converter (ADC). The sampled data can be subsequently processed using various DSP techniques known in the art.
Sample rate conversion generally refers to the process of converting samples at one rate to samples at a second rate. A sample rate conversion ratio refers to the ratio of the input sample rate to the output sample rate. Sample rate conversion may be necessitated, for example, by the need to support multiple industry standards. As an example, for digital audio, many sources are sampled at a sample rate of either 48.0 KHz or 44.1 KHz. It may subsequently be necessary to process data that has been sampled at one rate (e.g., 48.0 KHz) to generate resampled data at a second rate (e.g., 44.1 KHz). For this example, the sample rate conversion ratio is 48.0/44.1, or 160/147 (which is the lowest common denominator for 48,000/44,100).
Often times, for ease of processing, it is desirable to represent the sample rate conversion ratio as a "fractional binary ratio" having a denominator that is a power of two (e.g., 16,384 or 2.sup.14). However, as illustrated by the example above, the sample rate conversion ratios for some applications cannot be exactly represented with fractional binary ratios. When this occurs, one conventional technique simply approximates the sample rate conversion ratio with a nearly equivalent fractional binary ratio, and ignores the resulting error. For the example described above, a fractional binary value of 17832/16384 can be used to approximate 160/147, with a resulting error of 136/(16384.multidot.160). However, this technique is inadequate for applications that require precise sample rate conversion ratios.